Ulna, extraarticular, metaphyseal simple (AO/OTA 2U1A2)

Simple extra-articular fractures of the ulna are classified as 2U1A2 fractures.

X-ray taken from Orozco R et al, (1998) Atlas of Internal Fixation. Used with kind permission.

The radial head can dislocate or subluxate posteriorly with respect to the capitellum (posterior Monteggia lesion). It’s uncommon to have a fracture in this location of the ulna without radial head dislocation and it’s uncommon to have a posterior dislocation of the radial head without fracture of the radial head.